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💡 From a breeze to a monsoon
Wind is simply air moving from high pressure to low pressure — and those pressure differences come from the Sun heating the Earth unevenly, from a hillside breeze to planet-wide winds.
How does uneven heating cause winds?
- Wind is the movement of air from a region of high pressure to a region of low pressure.
- These pressure differences are mainly caused by the uneven heating of the Earth’s surface by the Sun.
- Uneven heating of land and water also drives land and sea breezes; the same idea explains winds and ocean currents at every scale.
✅ Test Yourself
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How does a valley breeze form during the day?
Show answer
Sun-facing mountain slopes heat faster than the valley floor. The air over the slopes warms, rises and leaves a low pressure region, so cooler air from the valley flows up the slopes — that upslope flow is the valley breeze. -
What are gyres, and which way do they rotate in the Northern Hemisphere?
Show answer
Gyres are the large circular patterns formed when the Earth’s rotation deflects moving water masses. In the Northern Hemisphere they rotate clockwise, and counter clockwise in the Southern Hemisphere. -
Name the ocean current that keeps European ports ice-free in winter.
Show answer
The North Atlantic Drift, an extension of the Gulf Stream, which carries warm water towards the north-western coast of Europe.
What are the two kinds of wind?
Winds
Small area or global?
1. Local winds
Over a small area
Example:
Valley and mountain breeze
2. Planetary winds
Circle the whole globe
Example:
Trade winds
